Hemes labeled in selected positions with deuterium, tritium, or carbon-13 will be synthesized for use as NMR probes to gain an understanding of the relationship between hyperfine shifts and structure/function correlations in heme proteins such as myoglobins, hemoglobins, cytochromes, and peroxidases. The carbon-13 and deuterium labeled compounds will also be used for making definitive assignments in resonance Raman spectra. The synthetic compounds will be reconstituted into the appropriate proteins and will enable assignment of heme-associated resonances by difference spectroscopy for protons, and directly in the deuterium, tritium, and carbon-13 spectra. Two fundamental approaches will be followed in syntheses of the labeled hemes; carbon-13 and some deuterium labeled derivatives of protoporphyrin-IX will be obtained through total synthesis from acyclic precursors using our recently developed tripyrene approach, and cupric salt catalyzed cyclization of 1',8'-a,c-biladienes (the unusual mechanism of which will be studied). A mono-meso-deuterated derivative of protoporphyrin-IX will also be synthesized to test the validity of an NMR model for heme catabolism to bilirubin. The second route to labeled hemes will utilize deuterium or tritium exchange on protoporphyrin-IX and some of its relatives to give directly the required labeled compounds; an attempt will be made to rationalize the direct exchange processes on the basis of the electronic structure in the heme or free prophyrin nucleus. The primary uses for the deuterium labeled hemes will be in peak assignment in paramagnetic heme proteins, whereas the carbon-13 labeled compounds will be used for NMR studies of diamagnetic heme proteins, primarily. Certain novel unlabeled porphyrins will be synthesized so that they can be reconstituted, as hemes, into hemoglobin for X-ray studies to be carried out elsewhere.